环境电离模型辐射体源放射性核素活度浓度的HPGeγ谱仪就地测定

MEASUREMENT OF RADIONUCLIDE CONCENTRATION IN CYLINDRICAL VOLUME SOURCES USING AN IN-SITU HPGe γ SPECTROMETER

本工作建立了由圆柱型环境电离模型辐射体源发射的γ光子进入HPGeγ谱仪晶体发生相互作用以及γ光子能量沉积的物理数学模型 ,自编了蒙特卡罗 (MC)模拟软件GED8.FOR ;模拟计算了一台便携式就地HPGeγ谱仪 (54 .8mm× 57.9mm ,ε=30 .3%,FWHM =1.71keV)就地测量模型辐射体源内放射性核素活度浓度的校准因子。利用该谱仪对核工业放射性勘查计量站的圆柱型环境电离模型辐射体源内放射性核素活度浓度进行了就地测量分析 ,分别测得 10个模型辐射体源内放射性核素 ( 2 3 8U、2 2 6Ra、2 3 2 Th和40 K)的活度浓度值 ,并与上述模型辐射体源的取样分析结果进行比较。对各模型辐射体源内的主导放射性核素 (即所掺矿粉且含量较高的核素 )而言 ,两种方法的结果在± 6 .2 %的偏差范围内吻合 ;

A physical mathematical models for incident photons making interaction with HPGe crystal and depleting their energy into the crystal are established. GED8.FOR, a code of modeling the calibration factors for a in situ HPGe γ spectrometer to measure the activity concentration in a cylindrical volume source with Monte Carlo methods is developed. The calibration factors for an in situ HPGe γ spectrometer (the size of the Ge detector is  54.8 mm×57.9 mm, the relative detection efficiency is 30.3%, the resolution of energy is 1.71 keV at 1333 keV) are obtained with the code GED8.FOR. The activity concentrations of radionuclides, such as 238 U, 226 Ra, 232 Th and 40 K, in the 10 cylindrical volume sources, supplied by the Metrology Station of Radio Geological Survey of CNNC, are respectively measured by the in situ HPGe γ spectrometer. They are in agreement within the deviation of ±6.2% for main radionuclides, when the activity concentration measured by the in situ HPGe γ spectrometer are compared with that early analyzed in a laboratory.